The present disclosure relates to a seat structure for installation in a seat assembly and a method of making a seat structure for installation in a seat assembly.
Seat structures (e.g., seat back frames, seat base cushion frames, low seat structures, back frame seat belt towers, etc.) can provide strength to a seat assembly to meet strength and/or durability requirements that are regulated by governmental agencies (e.g., FMVSS) or dictated by vehicle manufacturers. Seat structures also can be configured to meet the desires of customers for seat assemblies to provide increased functionality or utility (e.g., rotating, folding, sliding) while maximizing user comfort. Achieving the desired structural (e.g., strength, stiffness, durability, etc.), functional, and utility characteristics typically requires the use of additional components, which can have an undesirable impact on mass, cost, and comfort. Seat structures are typically designed by balancing structural and functional characteristics against mass, comfort, and cost.
Conventionally, a seat structure may be constructed by forming a monolithic tube with constant cross sections, with constant thickness and constant outside parameter through a series of tube bending processes and then using a joining process (as gas metal arc welding (GMAW)) to couple support members to the formed tube through a series of manufacturing stations or work cells. The support members, having been formed by conventional stamping processes (e.g., a multiple station progressive stamping die), are typically used to provide attachment structures for other members (e.g., recliner, head rest, retractor, or other structure), or to provide additional strength in high stress areas. This method of construction has several disadvantages. First, the singular tube seat structure accommodates varying stress levels by either over-designing the tube in all regions of the tube so as to withstand the maximum stresses (increasing mass and cost), or by reinforcing the local high stress regions with additional structural components (increasing cost, the number of parts and the number of manufacturing processes). Second, the monolithic tube seat structure may limit design application or compromise design efficiency because of limited manufacturability. For example, the bend radius required for manufacturing a specific tube might drive an inefficient design or even limit the application of the design. Third, a method of constructing the monolithic tube seat structure requires significant part handling downstream in the manufacturing process, which adds to the cost per structure and to the overall tooling (fixture) cost. Fourth, the method of constructing the monolithic tube seat structure can inhibit optimization of mass and strength because the desire to reduce costs by having as few parts as possible in the assembly can cause manufacturers to structurally overdesign portions of the seat structure to achieve part reduction. Finally, some conventional methods of coupling (e.g., GMAW, fasteners) require overlaps and/or the addition of material, such as extra parts or filler material, which negatively impacts mass and cost.
A conventional seat back structure constructed using a round tube 8 is shown in FIG. 14. This construction illustrates the need to include members 10 to provide attachment of recliners and members 12 to provide attachment for headrests or other members. This conventional construction is inefficient with respect to mass and cost. The mass is increased since the attachment members may provide no additional strength beyond solely the attachment function. The cost is increased because the redundant attachment members increase cost per structure and the need to couple them to the structure increases manufacturing costs through handling and assembly.
There is a need to design and form structural components with reduced mass and reduced cost, while meeting or exceeding strength and durability requirements. Additionally, the cost to handle the component-increases significantly as a product moves downstream in its manufacturing cycle, hence there is a desire to reduce or eliminate downstream operations.